diff --git a/lib/private/Files/ObjectStore/S3ObjectTrait.php b/lib/private/Files/ObjectStore/S3ObjectTrait.php
index 9d692e01a23f1..a88ebbeda8234 100644
--- a/lib/private/Files/ObjectStore/S3ObjectTrait.php
+++ b/lib/private/Files/ObjectStore/S3ObjectTrait.php
@@ -152,7 +152,7 @@ public function writeObject($urn, $stream, string $mimetype = null) {
 		// ($psrStream->isSeekable() && $psrStream->getSize() !== null) evaluates to true for a On-Seekable stream
 		// so the optimisation does not apply
 		$buffer = new Psr7\Stream(fopen("php://memory", 'rwb+'));
-		Utils::copyToStream($psrStream, $buffer, $this->uploadPartSize);
+		Utils::copyToStream($psrStream, $buffer, $this->putSizeLimit);
 		$buffer->seek(0);
 		if ($buffer->getSize() < $this->putSizeLimit) {
 			// buffer is fully seekable, so use it directly for the small upload